Known in the art is a process for obtaining a half-tone picture of irregular structure, comprising consecutive steps of exposing a negative of phototechnical silver-halide material with an average linear size of silver halide microcrystals of less than 1 micron, developing in a conventional black-and-white developer, softening in hot water or another liquid to a state close to that of fusion of the photographic layer, rinsing in cooled (8.degree. to 10.degree. C.) water, reducing in a solution containing an oxidizing agent, e.g., potassium ferrocyanide, and intensifying in a uranium salt solution.
This process is disadvantageous in that the gelatine silver-halide photographic layer becomes mottled, which results in process instability depending on the degree of hardening, storage time, photographic layer thickness and temperature difference.
Also known is a process for obtaining a half-tone picture of irregular structure, which consists in exposing a silver-halide material with an average linear size of silver halide microcrystals of about 0.5 microns, developing the exposed material in a conventional black-and-white developer, preparing a mask by way of exposure of the resulting picture on a silver-halide material, developing the exposed material in a conventional developer, matching the mask with the resulting picture, printing the matched mask and picture on a high-contrast photosensitive material, and developing the exposed high-contrast photosensitive material in a high-contrast developer.
A disadvantage of this process is that the contrast of the obtained half-tone picture is too high, the process is complicated and difficult to control.
According to another known process for obtaining a half-tone picture of irregular structure, the following sequence of steps is carried out: exposure of a silver-halide material, e.g., X-ray film, with an average linear size of silver halide microcrystals of 0.9 to 1.0 microns, development of the exposed material in a metol-hydroquinone developer, printing of the resulting piciture on a high-contrast photosensitive material, and development of the exposed high-contrast photosensitive material.
A drawback of this prior art process is the impossibility of obtaining a picture with the optical densities of the original reproduced within an adequate range (L&gt;1.0) when use is made of the above material with an average microcrystal linear size of 0.9 to 1.0 microns and when the exposed material is developed in a metol-hydroquinone developer.